In the orthopaedic surgery field, several operations are intended to fix one tissue to another in order, for example, to facilitate the taking of a graft, to restore a natural link between tissues after the link has been damaged or destroyed by an illness or by trauma, to consolidate a bone or even to strengthen a broken joint.
In particular, the practice of fitting an arthrodesis, i.e., forced immobilisation of the joint in question by triggering a bony fusion between the bones which constitute the joint, is known with patients suffering from major articular lesions, in particular, severe arthritis which has led to damage to the cartilaginous and/or bony articular surfaces.
The arthrodesis can, for example, be fitted to inter-phalangeal joints, in particular, the foot, and employ different surgical techniques.
One exemplary surgical technique consists of resecting the ends of two consecutive phalanges which have to be fused in order to create surfaces termed “bleeding,” to place the bleeding surfaces obtained in contact with one another, and then to fit a fixing implant intended to facilitate regeneration of the bony tissues at the contact interface.
To this end, the introduction of a pin, i.e., a fine cylindrical metal rod in line with the medullary axis of the phalanges, wherein the pin crosses the joint from side to side and limits the radial movement of one phalange relative to the other, is known.
One variant of this technique consists of using a screw rather than a pin, the screw is from the end of the finger in line with the medullary axis of the distal phalange so as to cross the joint and support the two phalanges compressed against one another.
Although these arthrodesis implants generally are satisfactory in therapeutic terms, the arthrodesis implants, however, suffer from drawbacks that are not negligible related, in particular, to the quality of the mechanical link produced between the tissues, and, more particularly, between the bones which the arthrodesis implants are supposed to support.
Indeed, the above-mentioned implants provide only partial mechanical support for the first bone against the second, more particularly, for the first phalange relative to the second, which tends to retard and complicate the reconstitution of a bony tissue at the contact interface of the bones.
More precisely, if the patient moves the member in question, for example, when walking if this is an arthrodesis implanted in the foot, the mechanical stresses applied to the joint can be the source of unwanted relative movements of the bones which are liable to lead to tearing and abrasion of the tissue being formed.
For example, the bones are liable to slide along the pin and thus separate axially from one another or even to rotate about the axis formed by the pin. Similarly, a medullary screw may slacken under the effect of relative rotation of the first bone in relation to the second, while allowing relative movement of the bones.
Moreover, arthrodesis implants from the prior art generally expose the patient to trauma of the tissues of the joint located in the vicinity of the treated joint. Thus, a medullary pin is liable to move longitudinally until the pin is just supported against the cortical tissues or the soft tissues located in the lengthening of the axis of extension or even to perforate the tissues. The projection formed by the head of the screw comes into contact with the surrounding tissues of the joint and thus form a painful point of compression and causes premature wear of the tissues.
Next, the forced position in which the arthrodesis implants from the prior art block the joint frequently differs from the natural anatomy of the patient, which generates a situation of discomfort or even pain for the patient.
Finally, arthrodesis implants from the prior art generally need significant surgical preparation of the joint and are of significant bulk which tends to make the operation long, complex and traumatic for the patient.